Honeywell UDC2500 manual Procedure #8, Troubleshooting a RS-485 Communications Failure

Troubleshooting/Service

Procedure #8

Table 7-11explains how to troubleshoot a Communications failure

Table 7-12 Troubleshooting a RS-485 Communications Failure

Step

What to do

How to do it

1	Check the Address Number,	See Section 3.13.
	ComState and Baud Rate settings.
2	Check the field wiring and	Using an ohm meter, check the resistance across
	termination resistor.	the communications rear terminals. See Section
		2.7 for wiring diagrams.

3Make sure the Communications Printed Wiring Board is installed properly in the controller.

Withdraw the chassis from the case and inspect the board. See the exploded view (Figure 8-1)for location of the board. Return the chassis to the case.

4Determine if the Communications board is faulty by running a LOCAL LOOPBACK TEST.

If the test fails, replace the board. If the test passes, the problem is most likely elsewhere in the communications network.

Disconnect the communications cable from the rear terminals. Run the Local Loopback Test.

Press [SET UP] until you see:

Upper Display

SET UP

Lower Display

COM

Press [FUNCTION] until you see:

Upper Display

DISABLE

Lower Display

LOOPBACK

Press oryou will see:

Upper Display

ENABLE

Lower Display

LOOPBACK

The test will run until the operator disables it here.

172 UDC2500 Universal Digital Controller Product Manual 4/07